The present invention relates to the field of drainage line units and, more particularly, to machines and methods for the manufacture thereof.
Drainage line units have been available for a number of years. Various U.S. patents describe such units, as well as an apparatus for manufacturing the units, for example, machines for manufacturing drainage lines have been previously described in U.S. Pat. No. 5,154,543. Also, the drainage line units best suited for production by the apparatus of the present invention are as previously described in U.S. Pat. Nos. 5,015,123, 5,051,028, 5,154,543, 5,535,499 (the ""499 patent) and 5,657,527 (the ""527 patent).
The previously disclosed and patented apparatus for fabricating the drainage line units, shown in the ""527 and ""499 patents, relied on machines using mechanical means to push an artificial aggregate material through a mandrel into a sleeve of netting to form the drainage units. The preferred artificial aggregate has been polystyrene or other poly-resinous material, however, as described in the ""527 patent, these materials exhibit a high coefficient of friction, which makes it difficult to move this material through a conduit in a manufacturing operation. Mechanical means of pushing the aggregate included a hydraulically operated piston device and a screw drive auger, as shown in FIG. 15 of the ""527 patent.
Experience with the manufacturing equipment shown in attached FIGS. 13, 14 and 15 of the ""527 has shown that when using polystyrene and similar poly-resinous materials for the aggregate 21, the aggregate exhibits a high degree of surface friction when compacted by operation of the reciprocating hydraulic piston 101. To this end, it has been determined that the direction of compaction is not only longitudinally along the length of the mandrel 91, or conduit, but also that the nature of polystyrene and other poly-resinous materials is such as to expand outwardly into a high friction engagement with the inner surface of the conduit (mandrel 91). This problem occurs no only at the exit end of the mandrel 91, but also at intermediate points along its length, as is depicted in the cross-sectional side view of FIG. 18. In order to solve these problems, it was determined that the application of a low friction coating 250 along the inside surface of the mandrel 91, or conduit, substantially reduces the friction produced by the aggregate material inside the mandrel or conduit. Suitable low friction coatings include a silicone lubricant, or a deposited coating of a low friction polyresin such as nylon or Teflon(copyright) (a trademark of the DuPont Company). The use of the low friction coating dramatically increased the speed at which the hydraulic piston of the prior art could be reciprocated, thereby increasing the productivity of each manufacturing machine.
Rather than being directed at mitigating friction, the present invention overcomes the problems altogether through a new process, thereby resulting in much improved production rates and eliminating the need for lubricants or other means of mitigating friction between the poly-resinous material and the manufacturing equipment.
With the foregoing in mind, the present invention advantageously provides an apparatus for manufacturing a drainage line unit.
The present invention comprises transporting the poly-resinous aggregate material, such as polystyrene, through a conduit by creating a high velocity air flow within the conduit, thereby to pick up and transport the aggregate bodies through the conduit and within the air stream. The preferred aggregate is a light-weight material such as expanded polystyrene, other poly-resinous plastics, and any other light-weight materials suitable for crush protection in packaging and of an approximate size of xc2xe to one inch bodies, an example of which is the plastic foam material popularly known as xe2x80x9cpacking peanutsxe2x80x9d.
The high-velocity air flow provides a number of advantages over mechanical conveyance means. A high-velocity air flow lifts and carries the aggregate bodies through the conduit without producing significant friction. Less friction means that less heat is generated during operations. While mechanical conveyance devices, such as the piston or auger drives previously described, tend to produce breakage of the aggregate bodies, such effect is minimized when the means of conveyance is an air flow, therefore more of the aggregate is usable for the manufacturing application. In addition, a high-velocity air flow is produced more efficiently than driving mechanical means, using less energy, and therefore results in a less expansive manufacturing operation.
The apparatus of the present invention includes a support frame, a mandrel preferably shaped in the form of a tube and horizontally positioned on the support. The mandrel has a tube wall which defines an inner cavity, and includes rear, upper and front openings which communicate with the cavity. A controller connects to at least one sensor positioned relative to a direction of manufacture so as to provide sensing information to the controller, the controller operably connected to control the apparatus responsively to the sensing information. A pipe feeder feeds a predetermined length of perforated vent pipe through the inner cavity of the mandrel in a direction of manufacture from the rear opening to the front opening and therethrough. The pipe extends into the inner cavity so as to define a void space between the pipe and the wall of the mandrel. A hopper assembly connects to the mandrel and has an exit port positioned in communication with the inner cavity for therethrough feeding a plurality of plastic bodies into the cavity. A blower connects in communication with the inner cavity of the mandrel for producing a sufficient air flow therethrough for moving the plurality of plastic bodies to substantially fill the void space so that the pipe emerges from the front opening of the mandrel surrounded by the plurality of plastic bodies. A sleeve feeder connects to the mandrel for feeding a continuous sleeve of netting over the plurality of plastic bodies and the vent pipe emerging thorough the front opening of the mandrel, thereby substantially encasing the plurality of plastic bodies around the vent pipe to form a drainage line. A separator connects in responsive communication with the controller, and is positioned relative to the direction of manufacture downstream from the sleeve feeder for fastening the continuous sleeve of netting to the vent pipe as the pipe emerges through the front opening of the mandrel, so as to substantially encase the plurality of plastic bodies around the vent pipe. Following the fastening operation, the separator cuts the continuous sleeve, thereby forming a drainage line unit.